A protective gas welding torch for a known apparatus for cleaning (EP 0 090 233 B1) consists of a contact tube which leads a welding wire during cleaning, and a tubular gas nozzle which surrounds the gas nozzle at a distance and conducts an inert gas. The gas nozzle is provided with a conically tapered gas tip. In addition, the contact tube is also conically tapered at the end in the form of a truncated cone.
This known cleaning apparatus is provided with a controlled, rotatably driven cleaning head that is equipped with at least one co-rotating cleaning element, as well as with a supply and centering device for a coaxial positioning of the gas nozzle with respect to the rotational axis of the cleaning head in the area of at least one cleaning element.
Specifically, the gas nozzle to be cleaned is inserted up to a stop into a rotationally fixed nozzle holder and it is thus centered. At the same time, flushing wings are introduced into the interior of the gas nozzle, which are slidably pressed while scraping with a rotating cleaning head against the outer surface of the contact tube and the inner surface of the gas nozzle. The surfaces are thus cleaned in this manner of traces of debris and of welding spatter. For the flushing wings are in this case preferably used spring-loaded scraper elements. In addition, a pivotably mounted angle Lever can be also used, whose scraper surface is pressed by centrifugal force radially to the interior part for cleaning of the contact tube. This angle lever is also coupled by means of a spring to another flushing wing which is used for cleaning the inner side of the gas nozzle. This specific arrangement does not appear to be practical because without a rotary movement and without centrifugal force, the flushing wing regions to be introduced into gas nozzle will be spread further than the nozzle opening, so that it is then not possible to introduce them inside without additional measures and without a collision with the gas nozzle when the gas nozzle is inserted into the nozzle holder.
In addition, CMT welding (derived from Cold Metal Transfer) is known as a special type of a protective gas process which can be used in particular as a CMT Braze+process for CMT brazing welding in car body construction. An extremely narrow conical design of a gas nozzle is used for this purpose, wherein the protective gas exits at a high velocity and causes a constriction of the of the electric arc, so that a high welding speed can be achieved with a reduced gas consumption.
Due to the extremely conical design of such a gas nozzle, it is very difficult to reach for practical purposes the interior surfaces of the gas nozzle forming an undercut on the inner surfaces of the gas nozzle, and thus it is very difficult to clean them mechanically. Therefore, expensive ultrasonic cleaning is currently used. With robot-based welding, welding/soldering processes and process-integrated automatic cleaning is used with ultrasonic cleaning, which is particularly costly and complicated and requires high investment costs.